Title: Prediction of Crude Fat Content of Longissimus Muscle of Beef Using the Ratio of Fat Area Calculated by Computer Image Analysis: Comparison of Regression Equations for Prediction Using Different Input Devices at ...

Interpretive Summary: Marbling score is considered a measure of meat quality which reflects the amount and distribution of fat particles in meat. Marbling score is assigned by an inspector on a subjective basis. The purpose of this study of 158 ribeye muscles was to develop a way to predict actual fat content of ribeye steaks using photographs of a cross section of the ribeye muscle. The photograph shows the distribution and contours of the fat particles fo that slice of the steak. The technique of computer image analysis was used to calculate the ratio of area of the fat particles to the total area of the cross section of the steak. That ratio was then used to develop an equation to predict actual fat content. The equation using the computer predicted area explained 96% of the variation in actual fat content. Two different methods of photographing the cross section gave similar favorable results. Computer image analysis of cross section of ribeye steaks seems to ohave potential for objective prediction of fat content without chemical analysis.

Technical Abstract:
Crude fat content of longissimus dorsi (ribeye) muscle of beef cattle was predicted from a ratio of fat area (RFA) to area of ribeye muscle calculated by computer image analysis (CIA). Cross sections of 64 ribeyes taken at 6-7th rib from cattle at experiment station A and of 94 ribeyes from cattle at experiment station B were used. Crude fat content was determined for each muscle sample using petroleum ether and used as true fat content. A CCD camera was used as input device at station A, and a single-lens reflex camera was used at station B to photograph ribeyes for CIA. The contour comparison method, that assigns a threshold value for each marbling particle, was used to obtain accurate binarization. Minimum and maximum for chemical measurements of crude fat were 2.1 and 39.8%, and for RFA were 6.1 and 56.8%. This range covered almost the complete range of the Beef Marbling Standard used in carcass grading in Japan. The estimate of the equation for the regression of crude fat content (Y) on RFA (X) as calculated by CIA for all of the data was Y = .793X-3.04 with which explained .96% of variation. Regression equations for prediction of crude fat percentage from RFA for the two stations were Y = .741X-2.22 for station A, and Y = .782X-2.54 for station B. Both explained 91% of variation. Effects of experiment stations on intercepts and slopes were not significant (P > .10). The range of differences between actual and predicted crude fat content from the prediction equation, which was calculated without consideration of effects of stations, were -6.4 to 4.0%. The CIA of cross sections of the ribeye muscle seems to have potential for prediction of crude fat content.